Using museum and citizen-science data to monitor the range contraction of a threatened lizard species
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To assess the utility of museum and citizen-science databases in observing range dynamics of a species that is suspected to have experienced a significant contraction in recent decades, the Texas horned lizard (Phrynosoma cornutum). By integrating the spatial data from two sources, VertNet and iNaturalist, into a GIS computing environment and segregating observations by time periods, I calculated several metrics to characterize the size and location of the P. cornutum range over time. In particular I compared the location of the range edge for consecutive time periods so as to test whether the range has been contracting in each of the four cardinal directions. My study also illustrates a method that could be applied to other species that may be undergoing range contraction or expansion.